The most common wheel drive solutions on the market come from traditional motor manufacturers and mainly involve the integration of motor, transmission and wheel parts. Some also offer control electronics, which are generally integrated outside the motor-wheel assembly and in the most advanced cases into the motor. The safety wheel drive range now introduced by ez-Wheel integrates a motor and planetary gearbox and Li-ion batteries directly into a high performance cast iron wheel, as well as a control unit with SIL2/PLd and SIL3/PLe certified safety functions, a safety encoder and a safety communication interface based on the CANopen safety standard.

The safety control functions - usually referred to as Safe Motion Monitoring - are otherwise only installed in modern industrial motor controllers and larger systems for industrial automation. The complete integration of safe motion control functions into a motorized wheel is unprecedented in industrial motorization and is therefore now being presented as a world premiere.

The new range of self-contained ez-Wheel wheels is the most advanced mechanical integration on the market: a wheel with a diameter of 150 millimetres in a high-performance cast iron structure can move 700 kilograms. The manufacturer emphasizes the long service life of the two-stage planetary gearbox, which is integrated into the wheel hub. The frameless motor with high torque and low speed is installed directly in the housing. The 100 watt-hour Li-ion batteries with safe battery management are also embedded. Control electronics with a redundant motor encoder and an optional electric brake are integrated at the rear of the wheel drive.

The safety electronics offer certified control functions for the requirements of modern autonomous mobile robots: A SIL3/PLe (Safe Torque Off) mode to switch off the motor in case of danger, a SIL3/PLe (Safe Brake Control) mode to apply the parking brake, a SIL2/PLd mode with safe direction (SDI) to prohibit further travel in case of a frontal obstacle, a SIL2/PLd mode with safe speed limitation (SLS) to anticipate the risk of nearby obstacles, and finally the SIL2/PLd secured stop mode (SS1).

The drive wheels can be connected directly to the safety outputs of a laser scanner and form a fully safety-certified assembly without the need for other components. In terms of mechanical integration and system architecture, this product range offers significant advantages for mobile robotics in terms of space requirements, ease of implementation and overall cost. pb